DIY M119 engine top end work due to Timing Chain stretch - Mercedes-Benz Forum
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post #1 of 43 (permalink) Old 08-29-2010, 10:52 PM Thread Starter
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DIY M119 engine top end work due to Timing Chain stretch

There's enough info on various sites to DIY the various valve train components on the M119 engine, so the purpose of this post is to provide a few tips, some of which applies to the M119.98x only. I received much technical assistance from fellow member gsxr, as well as cheerleading from fellow member aam. I must say, he looks great in a skirt.


Timing chain stretch, the easy way (though less precise). This applies to ALL M119 engines.

The official way requires checking the timing stretch using a gauge to detect valve positions, but gsxr taught me a very easy, though much less precise, way of checking the stretch. (Btw, timing chains don't stretch so much as the holes on the links wear out and become bigger, and therefore the length of the chain assembly becomes longer.)

Step 1. Remove the right valve cover. DO NOT REMOVE OR SLACKEN THE TIMING CHAIN TENSIONER.

Step 2. Turn the engine (always clock-wise when standing in front of the car, staring at the car looking toward the rear), until the timing marks on the bell housing (harmonic balancer) reads 45°. (This is positions the engine to 45° before TDC @ cylinder 1.)

Step 3. At this point, you'll be 50/50 lucky. The camshaft turns half revolution for every time the crankshaft turns full circle. So every full rotation of the bell housing, you'll find that the cam shaft turns half.

Two ways to tell. One, see my picture of Step 1. If the cam lobes are pointing EXACTLY as the picture, then you're fine. Second, you'll find that the camshaft cog has little holes about 5-6mm drilled into it. There are several, and they all look the same, except one. That special one can be identified with some careful observation.

Step 4. When the chain is brand new (zero stretch), at 45° TDC, you should be able to put a 5-5.5 mm pin through the camshaft journey and into these special holes on the camshaft cog, at ALL 4 camshafts. I've used the valve cover bolt, and even allen wrench keys.

When there is chain stretch, each camshaft will be slightly off from one another, so you'll be able to get in only 2 or 3 at a time. However, for this exercise, you'll pin ONLY the right, exhaust camshaft (the right-most camshaft on the engine).

Since your chain should be stretched, you'll not be able to place the pin thru the cog. Turn the engine by hand until the pin easily goes in. Slowly nudge the crankshaft clock-wise by a degree or two until the pin goes in.

Step 5. Once it does, the pin will wiggle around a bit, so wiggle the pin left and right while turning the engine until the wiggle is more or less symmetrical (centered about the axis of the camshaft). At that point, read the number at the bell housing. Mine reads 3.5° past 45°, so the last camshaft is 3.5° late. Do this again several times (pulling the pin out and turning the crankshaft twice) to see if you can reproduce the number.

This is a ball-park method, but far easier to do. There's no official number for how much the timing can stretch, but I've read 6 degrees is the max.

Writing this up took longer than I expected, so I'll post other tips here next time.
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Last edited by jsap; 09-04-2010 at 10:09 PM. Reason: For quality
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post #2 of 43 (permalink) Old 08-30-2010, 03:02 AM
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Very useful write up and photos We'll have to archive it somewhere for easy reference. It always happens that someone needs the information in the future, and then there's the battle to find it.

BTW If you don't have a º degree symbol on your keyboard, I'll gladly replace the * with º

No trees were harmed creating this message, however some electrons were very inconvenienced.
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post #3 of 43 (permalink) Old 08-30-2010, 08:39 AM
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very good details with pictures, I really like that

Did you camshaft chain plastic guide rails (all about 10 units) are in good shape?
Normally some will broke in a tiny pieces and clog in the oil hole that make engine overheat
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post #4 of 43 (permalink) Old 08-30-2010, 11:56 AM Thread Starter
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Quote:
Originally Posted by RedLiner View Post
BTW If you don't have a º degree symbol on your keyboard, I'll gladly replace the * with º
Man, you just had me searching half the morning for the "°" on my keyboard!

Kidding. I'm just lazy. Here's a DIY on that:

° Degree Symbol DIY

Step 1. Make sure the "NumLock" on the numeric keypad is off.
Step 2. Hold down the "Alt" key.
Step 3. While holding down the "Alt" key (step 2), push these numbers on the keypad in this exact sequence: "0," "1," "7," "6"

This procedure is often expressed as "Alt+0176"

If you're having trouble, take your keyboard to your dealer, and make sure they check your fluids and tire pressure.

Quote:
Originally Posted by Dostrix View Post
Did you camshaft chain plastic guide rails (all about 10 units) are in good shape?
Yup, all are good. I replaced all of them over the years, except for that lower one by the crankshaft. That requires pulling the water pump and harmonic balancer, so I skipped it. The failure mode on these guide are fracturing at the pin locations, and the lower one is by far the biggest and beefiest, so I'm not expecting failure anytime soon.

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Originally Posted by Dostrix View Post
Normally some will broke in a tiny pieces and clog in the oil hole that make engine overheat
Is this why you decided to overhaul your engine, to clear the oil galleries? How did the pieces get past the oil pickup screen? Do tell! The more I get into these engines, the more fun it gets.

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Last edited by jsap; 09-04-2010 at 10:10 PM. Reason: Changed "crank" for "drive"
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post #5 of 43 (permalink) Old 08-30-2010, 12:14 PM
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Has anyone ever heard of a 119 motor timing chain stretched beyond spec?
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post #6 of 43 (permalink) Old 08-30-2010, 09:03 PM
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Quote:
Originally Posted by jsap View Post
Is this why you decided to overhaul your engine, to clear the oil galleries? How did the pieces get past the oil pickup screen? Do tell! The more I get into these engines, the more fun it gets.
Look good for your DIY, really like it

My main problem for overhaul is the crankshaft is crooked, the other parts are just change by the age of 17 years that have to change, especially the gaskets that makes water and cylinder almost leak to each other

For the chamshaft plastic guide rails, when it broke it will stuck on the way to the oil pump, not even run to the pick up screen yet
I heard many of M119s that overheat from this problem
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post #7 of 43 (permalink) Old 08-17-2011, 05:08 PM
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Fantastic writeup & photos, jsap! Thanks for sharing!



Quote:
Originally Posted by deanyel View Post
Has anyone ever heard of a 119 motor timing chain stretched beyond spec?
There is no published spec for M119 chain stretch. Mercedes did publish specs for chain stretch on some of their 6-cyl motors, the usual limit is 3-4, however this is based on measurements more towards the middle of the chain. The method which jsap described above for the M119 measures near the end of the chain, relative to the drive gear. To determine M119 stretch in the middle of the chain, simply measure both left AND right exhaust cams, and split the difference. If you measure 6 at the right (passenger) exhaust cam, the left will likely measure 3, so stretch between the two points will be approx 4.5.

I've only measured stretch on a few M119's. One was 6 at the right exhaust cam, and I rolled in a new chain. Another was 3 and I left it alone. A third was zero (yes, zero, all four cams pinned at 45!) which means a previous owner probably had a new chain put in at some point. My personal opinion is that 2-3 is probably normal after engine break-in (the FSM allows up to 2 deviation when measuring at the valves), and 3-4 is probably no reason for concern. At 5-6, I'd probably want to plan a chain replacement. At 8-10, it's overdue and should be replaced ASAP. YMMV, etc...


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post #8 of 43 (permalink) Old 01-26-2012, 06:20 PM
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Hats off to you jsap for this amazing dyi. I am going to look into changing my guide rails in next few weeks and while at it I will also see if there is any timing chain stretch and then consider replacing it if needed. My question to you and others that have done this are:
1. Should I change tensioner preventatively even if I dont have chain strech? I have read stories of tensioner breaking and causing expensive damage.

2. Is the method of changing of the chain in M119 as described in the excellent diy directions (link below) for M116/117. If so then I might attempt to change my own chain rather than asking indy.
PeachPartsWiki: M116/117 Timing Chain Replacement

Thanks
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post #9 of 43 (permalink) Old 02-01-2012, 08:51 PM
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Quote:
Originally Posted by Gadha1 View Post
1. Should I change tensioner preventatively even if I dont have chain strech? I have read stories of tensioner breaking and causing expensive damage.
I wouldn't, but if you're rolling in a new chain, a new tensioner is generally a good idea. I have heard of very few M119 tensioners failing.



Quote:
Originally Posted by Gadha1 View Post
2. Is the method of changing of the chain in M119 as described in the excellent diy directions (link below) for M116/117. If so then I might attempt to change my own chain rather than asking indy.
Replacing the M119 chain is nothing like the M117, it's significantly more difficult. See photo below. You can not use pliers to clamp the chain to the sprockets to avoid jumping teeth. The FSM procedure says to use the blue wedges along with pressing the chain to the sprocket by hand, but this is a joke... even with two people, I had the chain skip a tooth four times while rolling the chain in. NOT fun. If your chain is not significantly stretched, I wouldn't replace it... up to 3-4 at the passenger exhaust cam is fine, IMO. The one I replaced was 6 which I deemed a bit too much. There is no official factory spec, as noted above in post #7.
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post #10 of 43 (permalink) Old 02-02-2012, 12:32 AM
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Great post and pics well done


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